Applicant has previously invented apparatus for the treatment of cooling tower water to control scale, corrosion and biofilm, using electronic oxidation and ionization apparatus. The national stage of this invention, PCT/US97/00885, is U.S. application Ser. No. 08/983376, with an international filing date of Jan. 17, 1997, and the entire contents of this application are hereby incorporated by reference. The electronic oxidation and ionization apparatus is further disclosed in U.S. Pat. Nos. 5,007,994 and 5,603,843, the entire contents of which are hereby incorporated by reference. A divisional of U.S. Pat. No. 5,603,843 is U.S. application Ser. No. 09/252389, the entire contents of which are hereby incorporated by reference.
Condensing water loops are well known and used as coolant or mass heat transfer systems for such things as power plants. Generally, water loops comprise a cooling tower, a condenser system and a pump. In refrigeration cycles using condensing water loops, the function of the cooling tower is to cool condenser water after it has removed heat from the refrigerant in the condenser. In industrial processes, the condenser has the burden of condensing chemical products over a given temperature range from vapor to condensate. In power plants, the condensing water is used to draw heat from the spent steam driving the turbines. The cooling tower in each of these applications is a mass heat transfer device. In refrigeration and air conditioning systems, the colder the water is entering the condenser, the less energy required to power compressors on the refrigerant side of the condenser. In chemical product manufacturing, the colder the water, the more efficient the condensation process and therefore the greater the volume of product produced at a lower cost. In electrical power generation, the warmer the water, the less efficient the power generation, thereby depriving the facility of additional power sales. In all applications, the less fouling on the cooling tower surfaces and in the waterside condensing tubes, the more efficient, economical and long lasting the system will be.
Water in a condensing loop draws heat from the refrigerant/chemical product/steam as it passes through the condenser. In the cooling tower, the heated water is cooled by evaporation and the mixing of cooler make-up water. Cooling towers come in various types and sizes. For example, there are atmospheric towers, hyperbolic natural draft towers, counter flow and cross flow natural draft towers, mechanical draft towers using either forced draft or induced draft, and hybrid draft towers which are fan assisted natural draft towers. The common element in each is a reduction in temperature of the condensing water coming off the condenser and returning the water to the condenser as close to the design temperature as possible. In all types of cooling towers (except dry towers) evaporation is the means of cooling the water. The towers are designed to expose the maximum transient water surface to the maximum air flow for the longest possible period of time. As a result, a portion of the water in the loop is lost in this process when it is discharged into the atmosphere as hot moist vapor (the “plume”). The cooling tower is a device that takes heat out of the circulating water and discharges the heat into the atmosphere. Water volume lost in this process is replaced by new water introduced into the basin of the cooling tower by means of make-up water piping to maintain a constant volume of water in the system.
Description of the Water Chemistry of Condensing Water Loops:
A description of the water chemistry of the condensing water loop has three components. The first component is the water chemistry of the make-up water. The source of the water will determine some of the dissolved solids and gases, colloidal solids, and suspended solids in the condensing water loop. Typical among these are dissolved forms of carbon dioxide (carbonic acid, bicarbonate ion and carbonate ion), calcium, sulfates, silica, chlorine or bromine compounds from purification efforts, nitrogen compounds, dissolved oxygen and hydrogen sulfide, and the hydrated oxides of iron and manganese (See Table 1). If the make-up is treated waste water or reused process water, it may also contain phosphates. Another source of the make-up water may be treated or untreated ground water or lake water.
TABLE 1Common Ions Found in Make-up WatercalciumCa++bicarbonatesHCO3−magnesiumMg++chlorideC1−sodiumNa+sulfateSO4−ironFe++nitrateNO4−manganeseMn++carbonateCO4−copperCu++phosphatePO4−
The second component in the water chemistry is the air borne particles and gases in the ambient air. The design and function of cooling towers insures that the water circulating through them will scrub gases and particles from the air passing through the tower. In addition to the normal atmospheric gases, the ambient air may also contain sulphur dioxide and ammonia. Solids of silts (silica), salts, clays (alumina), ash, and organic solids such as pollen, leaves, molds, bacteria, and spores of other living organisms are also contained in the ambient air.
The third source of components for water chemistry of the water in the condensing loop is the piping, valves, pumps, and equipment (including the condenser, tower, and basin) with which the water comes in contact while circulating. Also included in this component, are the chemical or organic compounds added to the water to control scale and corrosion. Condensing water loop piping is usually a system incorporating several different metals, including mild steel, brass, copper, stainless and galvanized steel. The cooling tower often will have pressure treated woods, concrete, plastic, and asbestos that will contact the water as it circulates. Salts, liquids or gases of chlorine or bromine, chromate compounds, and magnesium compounds may be added to the water to control bacteria, algae, corrosion or scale. Since the water is the closest to a universal solvent, it will tend to dissolve a little of almost everything it comes in contact with. This leads to corrosion of system piping, valves and equipment creating compounds of zinc, copper, nickel and iron rust, leaching of arsenic and other compounds out of the cooling tower surfaces, and dissolving calcium compounds from concrete basins. As the water evaporates, the solids remain, increasing their concentration in the circulating water. The increased concentration accelerates corrosion, and coats the system's piping, valves and equipment. The heavier dissolved particles will settle out, primarily in the cooling tower basin and sump, but also in low pressure or restricted areas in the loop.
The accumulation of concentrated solids from the combined effects of evaporation, air scrubbing, leaching and corrosion together with the additive additions leads to a condition called “fouling.” The damp, warm, and dark conditions in the cooling tower and the basin leads to the rapid growth of algae, bacteria, fungus, and other organic compounds generally and commonly referred to as “biofilm.” The circulating water is rich in dissolved oxygen and other nutrients to further enhance the growth and spread of the biofilm. The biofilm tends to trap and hold the solids in the circulating water. This mass, when it settles to the bottom of the basin and the sump, becomes an insoluble and restricting sludge. Also, since some of the solids are the product of air borne pollution and the result of chemicals used for attempting to control biofilm, fouling, scale and corrosion, the sludge can contain potentially toxic levels of chemical compounds.
Description of Scale and Corrosion in the Condensing Loop System:
Scale, while being only one of the deposits that may form and be found on surfaces of the condensing water loop system, is generally the name given to all deposits found in the system. In fact, scale is defined as a deposit of a crystallization of a dissolved salt when its concentration exceeds its solubility. A true scale will re-dissolve without chemical change if the water composition is so altered that the water becomes unsaturated with respect to the precipitated compound. Condensing water loops will have scales of calcium carbonate, and calcium sulfate where sulfuric acid has been used for scale control. Calcium phosphate is often found in systems using sewage treatment effluent for makeup. Magnesium hydroxide is found in systems where magnesium is used as a corrosion inhibitor, and magnesium sulphate where sulphuric acid has been used for scale control. Barium sulphate is also found in systems where barium is used as a corrosion inhibitor and sulphuric acid is used for scale control. Sodium chloride deposits are often found in systems where chlorine has been used as an oxidizer for biofilm control. Where silica and silicates are in the water, they will combine with the other scale forming salts to create a very hard and particularly insoluble scale. The most common form of silica scale is calcium silicate which is a superior insulating material that can drastically reduce condenser thermal efficiency as well as restrict the flow through the heat exchanger.
Corrosion is an electrochemical process that takes place to some extent whenever a metal, water, and depolarizing agent are brought together. Any condition that causes one point on a metal surface to differ from another will permit corrosion to occur. The galvanic action of two different metals joined together in the presence of water will initiate corrosion on the more anodic of the two. Because corrosion is chemical, its rate increases with heat, therefore being the greatest in the condenser and on the condenser discharge side of the loop. Corrosion, like scale, is controllable and, to a limited extent, reversible with the proper maintenance of water chemistry balance.
Corrosion and scale are associated problems but the effect and cause should not be confused. The essential effect of corrosion is to destroy metal; scale, on the other hand, tends to clog open sections and to line surfaces with deposits. The products of corrosion often contribute to scale formation and aggravate the problem of its treatment.
Description of Fouling on Cooling System Operation:
Any film or deposit which forms on the waterside heat exchange surfaces reduces the heat exchange efficiency of the system (See Table 2). System efficiency is further reduced by maintenance shut downs for removal of deposits, and the repair or replacement of piping, valves, and equipment abraded by the suspended particles in the water or damaged by corrosion.
TABLE 2Heat Loss from Condenser Tube Scale (%)Scale Thickness InchesSoft CarbonateHard CarbonateHard Sulphate 1/50″ 3.55.23.0 1/32″ 7.08.36.0 1/25″ 8.09.99.0 1/20″10.011.211.0 1/16″12.512.612.6 1/12″15.014.314.3 1/9″—16.016.0⅛″—25.025.0¼″—50.050.0
Blowdown of the tower basin and sump has been the primary method of controlling the buildup of the suspended solids concentration in the circulating water. This process is expensive, wasteful of water, and potentially hazardous. The blowdown process requires that thousands of gallons of basin and sump water be dumped periodically and replaced with new make-up. Towers using municipal water supplies must purchase the make-up. The dumped water will also remove additives placed in the system to control biofilm, scale, and corrosion. Since some of these additives are potentially hazardous, the blowdown water must be discharged into approved sewers, with the accompanying costs, and must be monitored and reported, at an additional maintenance cost.
Another method employed to reduce or control the buildup of suspended solids in the condensing loop water is side-stream filtration. In this method, a portion of the circulating water (usually 1% to 10%) is drawn off and run through filters to remove the suspended solids. This method, while effecting the buildup of suspended solids, still requires the introduction of compounds to control biofilm, scale, and corrosion. Therefore, the filter discharge and the sludge will still contain potentially hazardous compounds requiring special discharge methods and controls.
Ozonization is also used in some systems and applications to replace chemical or organic biocides. Ozone, while an effective biocide, cannot by itself address all forms of organic matter which may foul the cooling water system. Ozonization will not eliminate the need for chemicals to control scale or corrosion. Unless used with side-stream filtration, blowdown will still be required to control the buildup of suspended solids. Potentially toxic compounds in the blowdown discharge (or filter discharge) and in the sump sludge will still exist with an ozonization system.
Magnetics, electrostatic charges and ultrasonic waves have also been used in some systems in a non-chemical attempt to control scale and corrosion. All of these methods still require the use of chemical or organic compounds for biofilm control, with the resulting potentially toxic blowdown and sump sludge discharge problems noted above. Also, unless coupled with side-stream filtration, none of these methods fully address the buildup of suspended solids.
As already noted, the introduction of chemical or organic oxidizers have been used as a method of controlling biofilm, but the oxidizers accelerate corrosion. Chemical oxidizers form potentially toxic compounds, while organic oxidizers do not form potentially toxic by-products.
To control scale and corrosion, some systems use chemical inhibitors. These chemicals are introduced into the circulating water to form insoluble oxides to coat the metallic surfaces to inhibit corrosion and provide a surface that is less likely to attract and hold scale forming compounds. These chemicals do not inhibit scale formation on the non-metallic surfaces of the cooling tower. The by-products of the scale inhibiting chemicals are potentially toxic, requiring expense for the discharge and control of the by-products. The chemical reaction with the circulating water results in new compounds being formed which add to the suspended solids burden of the water. The insoluble oxides formed to inhibit scale and corrosion, when deposited on the walls on the waterside condensing tubes, form an insulating layer, reducing the thermal efficiency of the condenser.
Another method of attempting to control scale and corrosion is the use of self-sacrificing magnesium anodes to coat the metallic surfaces with magnesium hydroxide to inhibit corrosion. Similar to the effects of the inhibiting chemicals noted above, magnesium hydroxide only inhibits corrosion of the metallic surfaces and it has no effect on the corrosive and leaching properties of the circulating water on the non-metallic surfaces of the tower and basin. Also similar to the chemical inhibitors, the magnesium hydroxide coating on the waterside of the condenser tubes is a thermal insulator decreasing the thermal efficiency of the condenser.
All existing methods of controlling fouling require (I) blow down, (ii) sanitary sewer or environmentally acceptable methods of discharging blowdown water or backwash water from side-stream filtration, (iii) expensive and time consuming additions of additives to control biofilm, scale, and corrosion, (iv) special procedures for the removal and disposal of sump sludge when potentially toxic compounds are precipitated as by-products of the chemical treatment to control biofilm, scale, or corrosion, and (v) the loss of thermal efficiency at both the waterside of the condenser and within the tower due to scale buildup. Even with inhibitors, periodic brushing of the condenser tubes and the tower surfaces is necessary to remove scale. When the method employed for the control of buildup of suspended solids is periodic blowdown, then the recurring buildup will abrade the surfaces of the condensing loop piping, valves, pumps, and condensers decreasing their design life and increasing maintenance costs.
U.S. application, Ser. No. 08/340,743 to Snee entitled “Electrical Water Purification Devises and Methods”, which is herein incorporated by reference, discloses a water purification system including (in one exemplary embodiment) a pair of electrodes, at least one of which comprises a plasma fused iridium coated titanium electrode used for the purpose of creating oxygen, hydrogen, and hydroxyl ions in the treatment of water; and according to another aspect of the invention, embodies a pair of copper electrodes to provide copper ions for the control of algae and bacteria. This Snee invention further provides a filtration and method of using these electrodes.
U.S. Pat. No. 5,007,994 to Snee, entitled “Water Purification System”, which is herein incorporated by reference, discloses a water purification system using a pair of carbon electrodes and a pair of copper electrodes submersed in the water to be filtered. When a potential is applied across these electrode pairs, the copper electrodes release copper ions, while the carbon cathode produces hydrogen ions and the carbon cathode produces oxygen ions. These ions produce a beneficial water treatment effect. Carbon electrodes are, however, subject to wear and have a limited life. The present invention provides an improved water treatment system and method.
As a related task of water treatment systems, Applicant has been testing its electronic oxidation and ionization apparatus in connection with pullet, layer and production facilities and has discovered major unexpected advantages to its method of treating water in connection with the health of the poultry. These advantages include decreased mortality, increased weight gain of pullets, lower feed conversion, better vaccine results, greater egg production, lower labor costs, lower maintenance, and easier operation of the processing plant.
As is well known in the art, poultry drinking water is provided by H2O lines connected to drinker cups and/or nipples. The drinker cups have a white ball attached to a nipple, which fill the drinker cup with water. Drinker nipples are held in place by water pressure in the H2O lines, so that they are normally closed. The bird pushes on the nipple to open the nipple to allow water to drip out. Scale formation has been a major problem in the past in connection with drinker cups and H2O lines. The valve mechanism includes a seat and ball, and scale forms between the seat and the ball, which prevents the nipple from closing, so that the drinking cup leaks. Leaking drinking cups cause several problems. First, the poultry are stacked in cages, so that if a drinking cup at the top of the stack is leaking, poultry below will get wet. Secondly, the manure on the ground will get wet, which is undesirable since this produces ammonia, which is hazardous to the poultry and maintenance personal. Also, the poultry does not consume the water fast enough and the remaining water becomes stagnant with a bad odor or leaks and drips on the poultry litter. The water in the drinker cups can also become contaminated with feces and bacterial growth. Chlorine cannot be used to clean the drinker cups because the poultry does not like the smell. The poultry will back off drinking water from the drinking cups and drink poor quality water elsewhere, which can make them sick, and causes them to eat less. The poultry gut flora gets destroyed so that the poultry cannot absorb nutrients correctly. The poultry can get secondary infections and suffer from dehydration. All of these health problems result in poorer quality poultry, and poultry with higher mortality rates.
The present invention provides a more efficient, economical and improved apparatus and method for the control of scale, corrosion and biofilm in a water system using electronic oxidation and ionization with side-stream filtration. The present invention also provides a method for treating poultry drinking water which solves the problems discussed above.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.